Dynamic fish completions breaks fish completions #2285

❯ ./result/bin/hei completion fish|source
- (line 3): Unsupported use of '='. In fish, please use 'set string hei'.
function __%!_(string=hei)perform_completion
               ^~~~~~~~~^
from sourcing file -
source: Error while reading file “<stdin>”

~/.local/share/fish/vendor_completions.d/toolname.fish (line 3): Unsupported use of '='. In fish, please use 'set string toolname'.
function __%!_(string=toolname)perform_completion
               ^~~~~~~~~~~~^
from sourcing file ~/.local/share/fish/vendor_completions.d/toolname.fish
	called on line 1 of file ~/.config/fish/conf.d/toolname-forwarding.fish
from sourcing file ~/.config/fish/conf.d/toolname-forwarding.fish
	called on line 223 of file embedded:config.fish
from sourcing file embedded:config.fish
	called during startup
source: Error while reading file '/Users/de13lb/.local/share/fish/vendor_completions.d/toolname.fish'